Conversion of hexaalkyldilead to tetraalkyllead



Patented June 5, 1951 CONVERSION OF HEXAALKYLDILEAD TO TETRAALKYLLEAD Ivar T. Krchn, Royal Oak, and Hymin Shapiro, Detroit, Mich, assignors to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application April 26, 1950, Serial No. 158,346

3 Claims.

This invention relates to the catalytic conversion of hexaalkyldilead to tetraalkyllead. It particularly relates to the conversion of hexaethyldilead, formed as a by-product in certain processes for making tetraethyllead, to tetraethyllead. It is, however, useful in converting other hexaalkyldileads, such as hexamethyldilead, hexapropyldilead and hexabutyldilead, to the corresponding tetraalkylleads.

Certain processes for making tetraethyllead. particularly those involving reducing metals other than sodium, such as magnesium, tend to form substantial quantities of hexaethyldilead in addition to or in place of the more important tetraethyllead product. Hexaethyldilead can be converted in part to tetraalkyllead by thermal treatment at temperatures above 80 C. as illustrated by the following equation:

It should be noted that based on the lead the theoretical conversion of hexaalkyldilead to tetraalkyllead is only 75 per cent. However, thermal treatment does not give the theoretical yield because to 40 per cent is lost to gaseous decomposition products which have little value. For example, in processes for making tetraethyllead, the tetraethyllead, by one method, is recovered from the other reaction products by steam distillation at about 100 C. At this temperature the hexaethyldilead present yields only 75 per cent of the theoretical yield of tetraethyllead, 25 per cent of gaseous decomposition products being formed. Thus a substantial amount of potential tetraethyllead is lost.

We have discovered that hexaalkyldileads can be converted to the corresponding tetraalkyllead products, with an efiiciency greater than that predicted by the theoretical equation above for the thermal treatment, by treating hexaethyldilead, at temperatures substantially below 80 0., even room temperature, with certain alkyl halides. Furthermore. the reaction of our invention proceeds without the formation of gaseous decomposition products.

The alkyl halide catalysts of our invention are the alkyl iodides and bromides, particularly the lower alkyl halides such as methyl, ethyl, propyl and butyl iodides and the corresponding bromides. Also by alkyl halides we do not mean to limit our invention to monohalides since polyhalides, such as dibromoethane, dibromopropane, dibromobutane and the corresponding dibromoiodides also can be used.

The time for the catalytic conversion of hexaalkyldilead varies between one-tenth to three hours and the temperature normally employed is from 20 C. to 100 C. The amount of catalyst employed varies from 5 to per cent of the hexaethyldilead being converted.

Our invention can be further understood by referring to the following working example.

To 5.8? grams of hexaethyldilead was added 1.7 grams of ethyl iodide. The mixture was heated for one and one-half hours at a temperature between and C. At the end of this period, analysis showed that 5.046 grams, or 98 per cent of the theoretical yield, of tetraethyllead was obtained. When ethyl bromide was substituted for ethyl iodide equally good yields were obtained. Likewise in a similar test dibromoethane converted over 9-8 per cent of the hexaethyldilead to tetraethyllead.

We claim:

1. A process for converting hexaalkyldilead into tetraalkyllead comprising treating said hexaalkyldilead with a material selected from the group consisting of alkyl iodides and alkyl bromides.

2. The process of claim 1 in which the material treated is hexaethyldilead.

3. The process of claim 2 in which the catalyst is an alkyl iodide.

IVAR T. KROHN HYMIN SHAPIRO.

No references cited. 

1. A PROCESS FOR CONVERTING HEXAALKYLDILEAD INTO TETRAALKYLLEAD COMPRISING TREATING SAID HEXAALKYLIDILEAD WITH A MATERIAL SELECTED FROM THE GROUP CONSISTING OF ALKYL IODIDES AND ALKYL BROMINDES. 